This application relates to and claims priority to corresponding German Patent Application No. 100 51 706.4 filed on Oct. 18, 2000.
The invention relates to a mounting apparatus for an optical element and more particularly to a mounting apparatus for mounting a lens.
Optical elements, e.g. lenses, have to be installed and adjusted very precisely in relation to their mechanical reference, in particular, in lens systems for semiconductor lithography. It is thus the case, e.g. with lenses, that the optical axis has to be made to coincide as precisely as possible with the ideal mechanical axis.
The applicant""s earlier application P 199 08 554.4 dicloses a three-point mounting via solid-state rotary articulations with solid-state transitions which can be adjusted by manipulators. A three-point mounting is also known from U.S. Pat. No. 3,917,385.
The object of the present invention is to improve the hitherto known installation and adjustment mounting method by an integrated fine-tuning functional unit, in order to achieve higher positioning accuracy.
This object is achieved according to one aspect of the invention by a mounting apparatus for an optical element, having an inner mount and an outer mount, the inner mount being connected to the outer mount via three circumferentially distributed solid-state articulations, and manipulators, acting on the solid-state articulations, by means of which the inner mount can be displaced, wherein the solid-state articulations are T-shaped in cross section, with a T-bar and a T-support, attachment points between the inner mount and the outer mount being located in each case in the region of the outer ends of the T-bar, and the manipulators acting on the T-support in each case.
In particulary to a further aspect of the invention the mounting apparatus refers to an apparatus for mounting a lens in a projection lens system for semi-conductor lithography.
The mounted optical element is retained in a statically determined manner by the three circumferentially arranged attachment points. Adjustment at the T-shaped transitions of the solid-state articulations then makes it possible for the inner mount of the optical element to be locally lowered or raised on the circumference. If the T-supports are subjected to the same force and the same displacement direction at all three transitions, then the optical element is displaced along its optical axis (z axis). Different forces and/or displacements at the attachments can correct and/or adjust tilting of the optical axis.
A very advantageous design for mounting the optical element may reside in the fact that the inner mount, the outer mount and the solid-state articulations are formed in one piece, and are separated off from one another by severing cuts.
The severing cuts may be produced, for example, by erosion.
A very advantageous application area for the apparatus according to the invention is in lense systems in which optical elements, in their installed position, deviate from the axis of gravity, i.e. from the vertical. This is because, in this case, the optical element, on account of its dead weight, tends to tilt in relation to the mechanical reference, in particular in the case of flexible attachments. The apparatus according to the invention then makes it possible, by means of sensors which are accessible and/or installed, for example, from the outside, to establish the deviating position and then to adjust the optical element back into its original position again.
With a suitable design of, and accessibility to, the manipulators, which may have, for example, hydraulic, pneumatic, mechanical or electrical actuating members, it is also possible for the apparatus according to the invention to be utilized actively in the optical functional group, in order for it to be possible to adjust image errors which occur during operation.